Fix Pages deployment and docs navigation

[mhmdaskari]

Summary

• Enables cleaner GitHub Pages deployment by fetching full history for the revision-date plugin.
• Updates the official Pages workflow actions to their current Node 24 major versions.
• Skips the deploy job outside main, so manual branch validation can build the docs without being rejected by the protected github-pages environment.
• Splits the generated API reference into a nested MkDocs tree for configuration, data, preprocessing, augmentation, framework models, plotting, CLI, and constants.
• Excludes .ipynb files from GitHub Linguist language detection so the repository language bar emphasizes Python rather than notebooks.

Deployment note

The repository Pages setting has also been enabled through the GitHub Pages API with build_type=workflow, which fixes the Get Pages site failed / Not Found error from actions/configure-pages.

Validation

• CUDA_VISIBLE_DEVICES=-1 mkdocs build --strict
• git check-attr linguist-detectable -- notebooks/00_data_postprocessing.ipynb
• Verified GitHub Pages API now reports build_type: workflow for https://mhmdaskari.github.io/EEG_DL_Classification/.